To a drive system of a railroad vehicle, provided is a gear device for reducing speed of and transmitting to an axle, a rotation of an electric motor. The gear device is generally constructed so as to be contained in a gear box to be mounted to a carriage in a state that a small gear of an electric motor side and a big gear of an axle side are engaged with each other. In such a gear device, provided is a breather device for reducing a difference between a pressure of an inside and a pressure of an outside of the gear box. The breather device is a so-called open-type one where the inside and outside of the gear box are connected with each other by a breather pathway (for example, see Patent Literature 1). Also, there is a breather device provided to a crankcase of an internal combustion engine. In the breather device, mounted is a valve system or the like which opens and closes the breather pathway as necessary (for example, see Patent Literature 2).